The invention relates to a refining surface of a refiner for a refiner intended for defibrating lignocellulose-containing material, which refining surface has a feed edge directed in the direction of the feed flow of the material to be refined and a discharge edge directed in the direction of the discharge flow of the refined material and which refining surface comprises at least one first blade groove and at least one second blade groove, between which there is a blade bar.
Further, the invention relates to a blade segment of a refining surface for a refiner intended for defibrating lignocellulose-containing material, which blade segment is arrangeable to form a part of the refining surface of the refiner and which blade segment has a refining surface of the blade segment, the refining surface having a feed edge directed in the direction of the feed flow of the material to be refined and a discharge edge directed in the direction of the discharge flow of the refined material, and the refining surface of the blade segment comprising at least one first blade groove and at least one second blade groove, between which there is a blade bar.
Further, the invention relates to a refiner for defibrating lignocellulose-containing material.
Refiners used for manufacturing mechanical pulp typically comprise two or more refiner elements positioned oppositely and rotating relative to each other. The fixed, i.e. stationary, refiner element is called the stator of the refiner, the rotating or rotatable refiner element being called the rotor of the refiner. In disc refiners, the refiner elements are disc-like, and in cone refiners, the refiner elements are conical. In addition to disc refiners and cone refiners, there are also what are called disc-cone refiners, where disc-like refiner elements come first in the flow direction of the material to be defibrated, and after them the material to be defibrated is refined further between conical refiner elements. Furthermore, there are also cylindrical refiners, where both the stator and the rotor of the refiner are cylindrical refiner elements. The refining surfaces of the refiner elements are formed by blade bars, i.e. bars, and blade grooves, i.e. grooves, between them. The task of the blade bars is to defibrate the lignocellulosic material, and the task of the blade grooves is to transport both material to be defibrated and material already defibrated on the refining surface. In disc refiners, which represent the most common refiner type, the material to be refined is usually fed through an opening in the middle of the stator, i.e. on the inner periphery of the refining surface of the stator, to the space between the refining surfaces of the refiner discs, i.e. to a blade gap. The refined material is discharged from the blade gap, from the outer periphery of the refining surfaces of the refiner discs, to be fed onwards in the pulp manufacturing process. The refining surfaces of the refiner discs may be either surfaces formed directly on the refiner discs, or they may be formed as separate blade segments positioned adjacent to each other in such a way that each blade segment forms a part of a continuous refining surface.
Usually, dams connecting two adjacent blade bars to each other are positioned at the bottom of the blade grooves of the refining surfaces of both the stator and the rotor of the refiner. The task of the dams is to guide material to be refined and material already refined to the space between the blade bars of opposite refining surfaces to be further refined. Since the dams guide the material to be refined to the space between opposite blade bars, refining the material can be promoted thanks to the dams. Simultaneously, however, the dams cause the steam flow taking the material to be refined onwards in the blade grooves to decrease, and prevent passage of the material to be refined and the material already refined on the refining surface by restricting the cross-sectional flow area of the blade grooves. This, in turn, leads to blockages on the refining surface, which then results in a decrease in the production capacity of the refiner, non-uniformity of the quality of the refined material and an increase in the energy consumed for the refining.
U.S. Pat. No. 4,166,584 discloses a refiner whose refining surfaces have blade bars. Between the blade bars, pocket-like structures are formed in the radial direction of the refining surfaces in such a way that the pocket-like structures in opposite refining surfaces are positioned partly staggered in the radial direction of the refining surfaces. Thus, the material to be refined may be moved, by the effect of the pocket-like structures, onwards on the refining surfaces of the refiner in such a way that the material to be refined moves from one pocket-like structure into the pocket-like structure on the opposite refining surface, hereby forcing the material to be refined to move into the blade gap and thus boosting the refining effect on the material to be refined.
U.S. Pat. No. 6,616,078 discloses a refiner whose refining surfaces have blade bars and between them blade grooves. The depth of the blade grooves in the feed zone of the refining surfaces is arranged to change in such a way that when the depth of the blade groove on one refining surface is great, the depth of the blade groove on the opposite refining surface is small at the corresponding point, i.e. the blade groove is shallow at this point, whereby the shallow portion of the groove forces the material to be refined to move to the opposite refining surface.
By means of the arrangements disclosed in both reference publications, guiding the material to be refined to the space between the refining surfaces can be boosted, and thus the refining effect can also be boosted. However, one weakness in both solutions is, for example, that the solutions affect to a large extent only the moving of the material to be refined in the depth direction of the refining surfaces from one refining surface to another refining surface. Thus, the movement of the material to be refined onwards in the blade gap remains rather inefficient in the case of these solutions. Further, since the change in the depth of the blade groove is implemented only in the feed zone in the case of U.S. Pat. No. 6,616,078, its effect in the area of the blade bars and the blade grooves, i.e. in the actual refining zone, remains insignificant.